We continue to progress in our studies of evolutionary and genetic problems with Drosophila as a test organism. (1) Our studies on the mechanism of DNA replication and repair deficient mutants is extended to chromosome III where ca. 60 mutagen sensitive mutants fall into 7 complementation groups. We also find that some of our X-linked mutagen sensitive mutants are sensitive to 4 different carcinogens. The biochemical basis of mutagen sensitivity is continuing. (2) We have identified the structural differences between slow and fast variants of ADH as a single amino acid difference. We are extending our analysis to other enzymes; e.g., alpha GPD and ACPH. (3) The analysis of mitotic recombination (MR) II chromosomes has been extended to 5 MR's of different geographical origin. All exhibit similar mutator activity for selected loci on the X chromosome. It has been demonstrated that MR functions in females as well as males. (4) Progress continues in the sterile male technique for natural population control. We are extending this technique to using translocations prefaced by a study of the fitness of homozygous and heteroygous translocations. (5) Field studies of the breeding biology of Hawaiian Drosophila species was extended and the larval substrates of several species uncovered. This should facilitate the laboratory rearing of these species, a prerequisite to planned hybridization experiments. Courtship behavior studies in the laboratory has been been extended to additional species.